Imaging technologies capable of acquiring a distance in the depth direction to an object (a depth map) as two-dimensional information include various techniques such as a technology of measuring the intensity and the return time of light reflected by an object by using reference light, a stereo distance measuring technology using multiple cameras, and the like. Depth map information allows more advance object recognition than image information acquired from normal cameras, and there is therefore a growing need for such depth map information as additional input information in relatively inexpensive products such as home electric appliances, game products, and industrial products.
Furthermore, among distance imaging techniques, there is known imaging devices with a compound-eye structure including an imaging lens that is a structure capable of acquiring a number of parallaxes by using a single camera and allowing distance measurement based on triangulation.
Sensor units such as cameras mounted on terminal devices such as portable terminals and cleaning robots are required to be capable of acquiring high-resolution, two-dimensional visible images, small and low in height (thin), and low in power consumption. Furthermore, in the future, new ways of using imaging modules with additional sophisticated functions such as gesture input and depth map acquisition are required in addition to visible image acquisition.
Cameras having a microlens array and multi-parallax passive depth map cameras such as a multiple-camera setup of related art can estimate distance without light sources (lasers, LEDs, etc.) and are therefore suitable for low power consuming, small devices driven by batteries, but are disadvantageous in principle in that distance cannot be measured when an object has no texture (difference in luminance).
In the meantime, when a system including active illumination means is used in a multi-parallax system such as a stereo camera, calibration of alignment between cameras and alignment between a camera and the active illumination means is required, and there is a disadvantage that occurrence of misalignment results in degradation in accuracy. Furthermore, when multiple systems are used, there is a disadvantage that a light source pattern emitted by one device may interfere with a light source pattern from another device, which causes an error.